1. Field of the Invention
This invention relates to data communication networks and particularly to networks having stackable repeaters.
2. Description of Prior Art
U.S. Pat. No. 5,189,414 describes a communication network having a repeater that is capable of coupling pairs of low-order networks, e.g., star couplers, to provide simultaneous data communication between two pairs of nodes, each node being coupled to a different low-order network. The invention is directed to solving the problem of prior art switching systems that coupled low-order networks through repeaters to a coupler that could switch one repeater to another repeater so that communication between only two nodes, each coupled to a different low-order network, was possible.
U.S. Pat. No. 5,115,235 discloses a number of slots in which modules are inserted to make contact with conductors on a backplane. To alleviate the need to rewire the backplane for each different functional module or inter-connection pattern, each module is fitted with two sets of switches, one set at each column of connectors to the backplane. The backplane connections comprise two columns of connectors, each column coupled to the adjacent column of connectors on the next adjacent module on each side. The switches can thereby control the signals coupled to the module or passed to the next adjacent modules. This solves the problem of having to rewire the backplane for different configurations of module interconnections and for modules performing different functions.
U.S. Pat. No. 5,079,766 describes a transceiver unit for coupling a Data Terminal Equipment (DTE) to a hub (repeater) for connection onto a transmission line. The transceivers with their associated DTE and the hub form an elementary segment. Circuits in the transceivers are included to supply send currents, to receive signals, and to provide collision detection. There is no capability of detaching the described elementary segment from the inter-segment (inter-repeater) transmission line.
U.S. Pat. 5,265,123 describes an expandable repeater for coupling a local network of DTEs to a bus for communications among local DTEs and DTEs in other local networks coupled to the bus. A commercial version of the described repeater is used in the implementation of the present invention as described in more detail below.
U.S. Pat. No. 4,674,085 shows the design of a network access device designed for simple daisy chaining with other devices to form a node for DTEs located in relatively close proximity, e.g., in the same room or on the same floor of a building, and sometimes referred to as Local Area Networks (LANs).
The systems shown in the above prior art references are useful for the purpose for which they were designed but do not address the problem of increasing collisions as the number of DTEs increases.
Available stackable hubs or repeaters must be assigned addresses using switches or plugboard arrangements when installed in a system. They must also be connected to a control device that cannot be removed. Addition or removal or replacement of a hub or repeater entails disabling the system and adjusting addresses of the hubs. The invention described below eliminates the drawbacks of prior art stackable hubs so that hubs in the stack can be removed or disabled without adversely affecting the operation of the other hubs in the stack or having to adjust hub addresses.